1. Field of the Invention
This invention relates to a method for identifying additional information for identifying a spectrally spread additional information superimposed on an information signal and a device for identifying a spectrally spread additional information superimposed on an information signal and for processing the information signal based on an identification result.
2. Description of Related Art
In the case that copyright of a producer is set in an information stored in a recording medium such as a magnetic tape or magnetic disk, duplication of such an information is prevented. Heretofore, processing of an information signal has been controlled in order to prevent duplication of the stored information in a recording medium by way of a method in which a spectrally spread specific additional information for specifying the producer is superimposed on the stored information signal and the additional information is identified.
For example, in such case, Japanese Patent Laid-Open No. Hei 1-149259 discloses a recording medium which is capable of detecting the producer's copyright without deterioration of the original audio signal quality by way of a method in which an additional signal for identification is spectrally spread and superimposed on the audio signal over the audio band.
In such case, a conventional information write device 1 shown in FIG. 1 which uses an additional information as an anti-duplication signal in order to prevent duplication is provided with a write section 2 for writing in a recording medium and an additional information signal detection section 3 connected to an input terminal t1 in parallel. A write control section 5 for controlling operation of the write section 2 is connected to the additional information signal detection section 3. The write control section 5 is connected to the write section 2, and a recording medium 6 in which an information signal is to be written through an output terminal t2 is connected to the write section 2.
In this conventional information write device 1, an anti-duplication signal has been added as an additional information signal on an information signal f1 supplied from the original recording medium, the information signal f1 is inputted to the write section 2 and the additional information signal detection section 3, and the additional information signal detection section 3 detects a spectrally spread additional information signal f2 superimposed on the information signal f1. Upon receiving the additional information signal f2 which the additional information signal detection section 3 detected, the write control section 5 supplies a write inhibition signal f3 to the write section 2.
The write section 2 where the information signal f1 is inputted writes the information signal f1 in the recording medium 6 if no write inhibition signal f3 is inputted from the write control section 5, and on the other hand, the write section 2 does not write the information signal f1 in the recording medium 6 and write operation is inhibited if a write inhibition signal f3 is supplied by the write control section 5.
In the above-mentioned conventional information write device 1, if an additional information f2 is superimposed on an information signal f1 from an original recording medium as described above, writing of the information signal f1 in recording media 6 is inhibited and duplication is prevented.
However, the conventional information write device 1 requires a long time to decode and detect the additional information, and is poor in detection accuracy of the additional information, and a high spread gain of spectral spread is required to ensure the detection. These conditions are disadvantageous.
The present invention is accomplished in view of the above-mentioned current problems of the additional information detection spectrally spread and superimposed on the information signal. The first purpose of the present invention is to provide a method for identifying an additional information which is capable of detecting an additional information spectrally spread and superimposed on the information signal with a small spread gain, within a short time, and with a good detection accuracy.
The second purpose of the present invention is to provide a device for identifying an additional information which is capable of detecting an additional information spectrally spread and superimposed on the information signal with a small spread gain, within a short time, and with a good detection accuracy, and performing processing of the information signal properly based on a detection result.